2. Recommendations for systematic screening for TB disease in targeted populations

In this guideline, recommendations about systematic screening for TB disease are made for distinct populations for whom it is judged that the benefits and desirable effects of screening outweigh the potential harms.

Systematic screening for TB disease can be done for an entire population (community-wide screening) or it can be targeted at selected risk groups or subpopulations of people who may be at higher risk of being exposed to TB, developing TB disease or suffering poor outcomes from the disease, or some combination of these. It can target people who seek health care (with or without symptoms or signs compatible with TB) and people who do not seek care (because they do not perceive that they have a health problem that warrants medical attention, barriers make it difficult to access health care, or for other reasons). Furthermore, screening can help identify people who are at particularly high risk of developing TB disease and thus may require repeat screening, for example, people with an abnormal CXR compatible with TB but who are not diagnosed with TB disease at the time of screening or people for whom TPT is recommended. Combining screening for TB with screening for TB risk factors can also help map individual- or community-level risk factors, comorbidities and socioeconomic determinants that need to be addressed to more effectively prevent the disease.

Strong recommendations are made for those risk groups or subpopulations for which the desirable effects of adhering to the recommendation are judged to clearly outweigh the undesirable effects: for these recommendations, screening is judged to be feasible, acceptable and affordable in all settings. Conditional recommendations are made for those risk groups for which the desirable effects of TB screening probably outweigh the undesirable effects, but the trade-offs, cost–effectiveness, feasibility or affordability, or a combination of these, are uncertain. Reasons for uncertainty may include a lack of high-quality evidence to support the recommendation; limited evidence of benefit from implementing the recommendation; high costs or low feasibility or acceptability, or a combination of these.

It is important that TB is diagnosed promptly in groups that have a particularly high likelihood of undetected TB or a high risk of poor health outcomes, or both, in the absence of early diagnosis and treatment, even if direct evidence of benefit from screening is lacking. This is the rationale for making strong recommendations despite a lack of high-quality direct evidence for some risk groups. However, prioritization should also consider the risks associated with screening, including false-positive diagnoses, overtreatment and the opportunity costs of screening in terms of the resources required, both across risk groups and in relation to other interventions aimed at improving early diagnosis, treatment and prevention. Therefore, owing to the lack of high-quality direct evidence comparing benefits with harms and on the cost–effectiveness of screening in many of the populations considered, many of the recommendations made for screening in specific populations are conditional.

The degree of uncertainty about the trade-offs between the desirable effects and undesirable effects varies across settings, and it depends on the epidemiological situation and the health system. Therefore, a conditional recommendation in this guideline implies that the appropriateness of adhering to the recommendation needs to be assessed in each setting, and there is a need to prioritize screening across risk groups in each setting.

For TB screening recommendations across all populations and in all settings, all people identified with presumptive TB disease should be offered HIV counselling and testing. In settings with a high prevalence of HIV, counselling and testing for HIV may be offered to all people screened for TB (8). People identified through screening who have symptoms or abnormalities suggestive of TB but who are not diagnosed with TB disease should be counselled and supported to seek medical care if their symptoms continue, emerge, re-emerge or worsen. If possible, repeat testing for TB should be offered to these individuals.

People who are diagnosed with TB disease through screening should have nutrition screening and assessment. If malnutrition is identified, it should be managed according to WHO’s recommendations on nutritional care and support for people with TB. Concerns about weight loss or failure to gain weight should trigger further clinical assessment (e.g. to determine whether there is resistance to TB drugs, poor adherence, comorbid conditions) and nutrition assessment in order to determine the most appropriate interventions (9).

Screening population groups at higher risk for TB is ethically sound as long as it designed and conducted to improve individual and public health and wellbeing; in this way screening contributes to the common good and upholds the ethical principle of accountability. As such, screening should always be done with the intent to provide care to those who need it, and never to exclude entry or employment or discriminate against individuals (10).

Nevertheless, screening population groups primarily based on risk raises a range of ethical issues (10). First, most of the individuals offered screening will not have TB disease and are not contagious. This makes the ethical obligations different from those associated with testing people who seek care because they are ill. For example, the absence of an immediate risk of transmission makes it unethical to restrict the movements of someone who has been offered screening. Refusal of screening should be respected and should not introduce discrimination of any sort. A screening programme should not create inequities in access to care for TB disease or any other reason.

Second, a positive screening test carries uncertainties, and confirmatory tests should be available to ensure an effective diagnostic pathway. Informed consent requires effective communication with each person about these uncertainties (e.g. false-positive results, risk of overtreatment). Appropriate mechanisms to obtain informed consent should comply with international human rights standards and account for different languages, literacy skills and legal status. Risk and uncertainty must be communicated in a way that is culturally and linguistically appropriate, including to those whose first language is foreign to the local setting, children, as well as to people in prison.

Third, TB disproportionately affects individuals and groups that are already disadvantaged due to disease, their socioeconomic situation or legal status, among other disadvantages. Therefore, efforts must be made to address existing inequities in access to services and to uphold human rights, so that the vulnerability of targeted groups does not impede their access to screening and treatment or violate their rights. Any intervention for vulnerable groups – including migrants, prisoners and children – should include measures to minimize the risk of stigmatization. Testing positive on a screening test – as with a confirmed diagnosis of TB – should not influence an immigration procedure or be used to force migration or deny entry to a country. Screening done for migration or employment reasons must uphold ethical principles; this should be reflected in laws or other policy regulations (10).

People should be offered screening in strict adherence to human rights and ethical considerations (11). Policies should be evaluated from an ethical perspective by those who use the guidelines, and the views and experiences of affected populations should be gathered after implementation, both to consider possible unexpected effects and to ensure that the evidence on which they are based remains current and relevant (12). Person-centred care entails, among other considerations, that it is provided in an equitable fashion without placing marginalized and vulnerable populations at an added disadvantage; it focuses on the human rights aspects of screening so that there are appropriate safeguards in law, policy and practice to minimize any additional stigma, discrimination, violation of bodily integrity or restrictions on freedom of movement; and people who are offered testing and treatment should understand the associated uncertainties, which will help them make decisions about care options. Established human rights principles, such as consent, noncoercion, and confidentiality, should be respected.

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